This study proposes to correlate the placental grade as described from real-time ultrasound examination with the impedance to blood flow in the fetal thoracic aorta, umbilical artery, and the accurate branches of the uterine artery, and the mean umbilical vein flow in a group of patients at risk for intrauterine growth retardation, based on clinical and historical factors between 26 and 42 weeks' gestation.